Method of molding utilizing thermosetting resins and magnetized filler material

ABSTRACT

Liquid resins and plastisols can be made to assume and hold desired shapes, or to bridge gaps, not attainable with the present commercially available filled liquid resins or plastic puttys by employing a &#39;&#39;&#39;&#39;filler&#39;&#39;&#39;&#39; material, which has magnetic property.

United States Patent Childress 1 June 6,1972

METHOD OF MOLDING UTILIZING THERMOSETTING RESINS AND MAGNETIZED FILLERMATERIAL Clyde 0. Childress, 3641 South Court St., Palo Alto, Calif.

Filed: Jan. 15, 1970 Appl. No.: 3,115

Inventor:

US. Cl ..260/37 EP, 260/37 R, 260/40 R Int. Cl ..C08g 51/04 Field ofSearch ..260/37 EP, 37 R, 38, 40;

References Cited UNITED STATES PATENTS l/1962 Creighton ..260/37 EP XMadison ..260/37 EP X Primary ExaminerLewis T. JacobsAttorney-Lindenberg, Freilich & Wasserman ABSTRACT Liquid resins andplastisols can be made to assume and hold desired shapes, or to bridgegaps, not attainable with the present commercially available filledliquid resins or plastic puttys by employing a filler" material, whichhas magnetic property.

5 Claims, 6 Drawing figures PATENTEDJUH 6 I972 //v VE/V TOR CLYDE O.CH/LDRESS By 9PM A A FOR/v5 Y5 METHOD OF MOLDING UTILIZING THERMOSETIINGRESINS AND MAGNETIZED FILLER MATERIAL BACKGROUND OF THE INVENTION Thisinvention relates to liquid resins and more particularly to a uniquefiller material for said resins.

It is common practice to use various metallic and other inert "fillermaterials in epoxy and similar resin systems. The addition of thesefiller materials is aimed primarily at conferring a putty-likeconsistency to the normally liquid resins, and thus to allow thicksections to be built up in a single operation and to prevent run downand sag when the resin is applied to a vertical surface. Commerciallyavailable filled resins do not generally achieve these objectives dueapparently to limitations on the amount of filler material that may beused without interfering with other required characteristics such aswetting the substrate, or obtaining the mixing consistency required toblend the resin and catalyst.

These commercial filled cements, marketed as body solders, body fillers,cement and filler, mender putty, and patch kits are generally suppliedin two parts, a resin and a catalyst. The filler may be incorporated inboth components or in the resin only when the catalyst is a smallportion of the total material. Epoxy resins are most commonly marketedin this form although polyesters and other resins are sometimes used.

The slow flow out of these commercially available materials, whenapplied in thick layers, generally requires a constant reforming of thelayer until it begins to cure. It is not possible to sculpt or shapesuch materials as one can with modeling clay or even with putty.

The wet or plastic dimensional stability of the filled resin cement,before it has set, is dependent on the viscosity of the resin and theadhesive forces exerted at the resin-particle interface. To achieve aputty like consistency with conventional inert filler materials it isnecessary to incorporate particles of very small size with consequentgreat surface area. Thorough blending of these fine particle fillerswith the liquid resin generally requires the use of roller mills orother such ap paratus. If sufficiently large quantities of very highsurface to volume fillers are incorporated to give good pre-cureddimensional stability to a liquid resin the liquid phase is so tightlyheld that the cement will not wet porous surfaces efi'ectively.

OBJECTS AND SUMMARY OF THE INVENTION An object of this invention is toprovide a novel filler material which enables one to build up thickerlayers of epoxy resin or other similar material, without flow out, thanhas heretofore been possible.

Another object of this invention is the provision of a filler materialwhich enables one to sculpt with a liquid epoxy resin, or similar resinsystem.

Another object of this invention is to provide a filler materia] whichimparts superior precured plastic dimensional stability to a liquidresin and which may be easily combined with a liquid resin withoutresorting to sophisticated mixing apparatus or tedious and exactingmanual mixing to ensure thorough wetting of the filler particles.

Another object of this invention is to provide a filler material forcombining with a liquid resin to form a paste or putty which exhibitsmore consistent plastic stability when the liquid phase is subject tochanges in viscosity due to exothermic cure reactions or applied heatused to accelerate the cure.

Another object of this invention is to provide a filler which does notsignificantly impair the ability of the incorporated resin to freely wetporous or deeply textured surfaces.

Still another object of the present invention is the provision of afiller material for a liquid resin whereby one can strengthen desiredregions of the cured composite structure which is formed.

The foregoing and other objects of the invention are achieved by using amagnetic filler material either in the form of a powder or filamentswhich are mixed with the liquid resin.

Magnetic materials that have been found effective in this inventioninclude ferromagnetic materials such as powdered Alnico 5 and choppedfine steel fibers as well as ferromagnetic materials such as magneticiron oxide and barium and strontium ferrite.

The concentration of magnetic filler material to liquid resin andcatalyst depends on the degree of plastic stability desired in theuncured state and upon the magnetic remanence, particle size and shape,and the specific gravity of the filler material as well as the flowcharacteristics of the liquid resin and catalyst portion of the mix. Inpractice, magnetic filler concentrations comprising from 10 to 60percent by volume have been found effective. With a medium viscosityresin and a magnetic filler of permanent ceramic magnet particles ofminus 200 mesh size, filler concentrations comprising 10 to 60 percentby volume have been found effective. At 10 to 20 percent the magneticfiller imparts plastic dimensional stability equal to or exceeding thatof typical commercial filled resin cements or putty containing 50percent filler concentrations, but unlike the commercial putty retainsvirtually the same ability as an unfilled resin to wet a poroussubstrate such as tightly woven glass cloth. Concentrations of magneticfiller from 20 to 50 percent by volume impart greatly superior plasticstability as compared with conventional fillers and yet may be extrudedfreely from a small opening in a dispensing tube. Above 50 percentconcentration the magnetic filler imparts a progressively moreplasticene" like workability that may be kneaded and formed into complexself-supporting shapes.

Other filler materials may be combined with the magnetic filler tochange the color or other characteristics of the material, providingsuch additions are not in sufficient quantity to negate the magneticcohesion imparted by the magnetic filler.

The filler particles of this invention may be magnetized before mixingor the applied magnetic field may be utilized to simultaneouslymagnetize and mix the particles with the resin. In some applicationswhere the resin and catalyst must be pressure fed continuously or ondemand it may be advantageous to mix and magnetize the filler at or nearthe point of exit to take advantage of the ease of delivery of theunfilled liquid components.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will best be understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the results achieved witha typical commercial filled epoxy cement used to patch or bridgecircular openings in a /a-inch thick board held in a vertical position.

FIG. 2 shows the results achieved with an epoxy resin into which therehas been mixed a filler material in accordance with this invention.

FIG. 3 shows the results achieved with a present commercial filled epoxyresin which was attempted to be formed into a vertical column.

FIG. 4 shows the result achieved with a liquid epoxy resin into whichthere has been mixed a filler material in accordance with thisinvention.

FIG. 5 shows the relative wetting ability of two commercial filled epoxycements or putties as contrasted with an epoxy cement mixed with amagnetic filler material in accordance with this invention.

FIG. 6 shows an arrangement for reinforcing desired regions of an epoxyresin into which there has been mixed a filler material in accordancewith this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In order to demonstrate theadvantages of this invention over the prior art it was attempted todetermine the maximum opening that could be patched or bridged in a/a-inch thick vertical wall with a commercial filled epoxy cement ascontrasted with a liquid epoxy resin mixed with a fine particle magneticfiller material.

FIG. 1 illustrates the appearance of a %-inch thick panel 10, withgraduated circular openings of 1 inch, one-half inch, and one-quarterinch respectively 12, 14, and 16, which have been patched or closed witha commercial filled epoxy cement. Within minutes most of this cement 18,has flowed out of the l-inch opening and out of the one-half inchopening 20, and only the cement 22 in the one-quarter inch opening hassuc' cessfully bridged the opening and retained its position long enoughto cure.

FIG. 2 illustrates the appearance of a duplicate of the structure ofFIG. 1 with the openings 26, 28, and 30 in the panel 24, filled with aliquid epoxy cement which has been mixed with a fine particle magneticmaterial in accordance with this invention. This magnetic epoxy cement32, has successfully bridged all three openings. The magnetic filleremployed was composed of sintered barium ferrite particles largely below74 microns in size. The filler comprised 43 percent by volume of themix.

Various commercial filled epoxy cements were tried and none successfullyspanned the l-inch and P -inch holes in the test shown in FIG. 1 andFIG. 2. V

In order to further demonstrate the advantages of this invention overthe prior art, it was attempted to determine the maximum verticalbuild-up that could be achieved with commercial filled epoxys ascontrasted with the vertical build-up achievable by mixing a fineparticle magnetic material with a liquid commercial epoxy. The epoxywith the conventional filler material, as well as the epoxy with themagnetic filler material were both sculpted into a vertical column whilestill in the uncured state.

FIG. 3 illustrates the appearance of the commercial epoxy putty andfiller which incorporates conventional filler materials. Within 5minutes after sculpting, the material collapsed into the form 34.

The commercial epoxy putty represented in this figure showed thegreatest degree of plastic stability of any of such commercial materialstested.

FIG. 4 illustrates the appearance of the vertical column which wassculpted from a liquid epoxy which was mixed with fine particle magneticmaterial in accordance with this invention. The magnetic filler employedwas pulverized permanent ceramic magnet particles below 74 microns insize in approximately an equal part by volume to the amount of epoxywhich was used. The column of material 36 shown in FIG. 4 maintained itsshape and dimension so successfully, that an opening 40 was alsosculpted to illustrate how effectively the material held its shape andhardened in the shape in which it was sculpted.

The superior plastic dimensional stability of uncured cementsincorporating the magnetic filler of this invention is apparently due tothe ability of the magnetic particles to actively align themselves intocohesive networks within the liquid resin. This active particle cohesiondoes not require the use of extremely fine powders with great surfacearea, consequently the filler particles may be relatively large andeasily dispersed in liquid resins without the use of roller mills orother such mixing apparatus. Since the cohesion of the magnetic particlefilled resin is less dependent on the viscosity of the resin to v bindthe particles its stability is consequently afiected to a lesser extendby changes in the viscosity of the resin due to exothermic reactionduring. the cure or when heat is applied to accelerate the cure.

In order to demonstrate the superior wetting" ability of the filledcement or putty of this invention contrasted with presently availablecements compounded with conventional fillers, a sheet of finely etchedground glass" was placed in intimate contact with a larger sheet ofplate glass and a small quantity of the cements to be tested weredeposited against the edge of the ground glass so as to allow the liquidphase of the cement to penetrate the'capillary opening between the glasssheets.

FIG. 5 shows the glass plate 42 and the juxtaposed ground glass sheet44. Deposits of two conventional filled epoxy cements or putties 46 and48 have been placed at the edge of the ground glass sheet, as well as adeposit 50 of a cement or putty mixed in accordance with this invention.The filled epoxy 46 represents the most free flowing of ten suchcommercial materials tested. The filled epoxy 48 represents the materialwith the best plastic dimensional stability of the 10 filled epoxycements tested. The liquid phase of the sample 46 has penetrated thecapillary space 52 between glass plates to a depth of approximately 2millimeters. The deposit of the more dimensionally stable material 48shows no significant penetration of the capillary space. The liquidphase of the material 50, which incorporates the magnetic filler of thisinvention, has penetrated the capillary space 54 to a depth of 5millimeters, showing greater wetting ability than the free flowingcommercial filled cement 46 even though it has greater dimensionalstability than either commercial material 46 or 48. The filler materialincorporated in the epoxy putty 50 is permanent ceramic magnet particleslargely between 37 and 74 microns in size and comprising 50 percent byvolume of the mix.

If the reinforcing filler material used in an epoxy or other such resinis present in the form of filaments, rather than a powder, and thesefilaments are magnetic, then an applied magnetic field may be used toselectively align the filaments so as to increase the strength of thefinal composite in the direction required to resist the expected maximumstress. Changes in the direction of the applied magnetic field can bemade relative to the cure rate of the resin or other binder in such amanner that the filaments in one layer of the material may be aligned atright angles to the next layer. Filaments may be oriented to producepatterns of three dimensional alignment within a solid or a complex thinwalled shape that may materially increase the strength as compared witha randomly oriented pattern of reinforcement.

FIG. 6 shows an arrangement of the type described wherein two pieces ofa metal bar respectively 56, 58, have placed therebetween epoxy 60 whichis mixedwith the magnetic filler material which has the form of fibers.The two poles respectively 62, 64 of a magnet are placed on either sideof the metal rod to align the filaments along the axis of the metal rod.This will have the efiect of increasing the resistance to bending of thefinished product at the region of the epoxy material, over what it wouldbe, should the epoxy be permitted to dry with the filaments morerandomly dispersed than is the case when the magnetic field is used toprovide the proper alignment.

In case of either fibers or powders, the application of a magnetic fieldto pull the filler material toward the carrier surface or mold formresults in a maximum concentration of reinforcing material and thereforeincreased strength. This technique may be of particular interest whenchopped fiber and resin and catalyst are sprayed" onto a form.

There has accordingly been described and shown a novel and useful meansfor mixing a liquid resin epoxy or other resin with a magnetic fillermaterial whereby the epoxy may be built up in thick layers withoutflowing and may be sculpted into self-supporting forms.

What is claimed is:

l. A method of forming shaped objects from flowable, curable, liquidresin materials comprising the steps of:

mixing said resin material with 10 to 60 percent by volume of aparticulate, magnetized, magnetic filler to form a plastic dispersionhaving increased, precured dimensional stability as compared to saidmaterial; shaping said dispersion into a self-supporting form; andcuring said resin into a dimensionally stable shape in said form. 2. Amethod according to claim 1 in which the resin is a liquid epoxy resin.

3. A method according to claim 2 in which the particles of magneticfiller are no more than 74 microns in size.

4. A method according to claim 5 in which the ceramic magnetic filler isselected from magnetic iron oxide, barium ferrite, and strontiumferrite.

5. The method as recited in claim 1 wherein said magnetic fillercomprises magnetic ceramic magnets.

2. A method according to claim 1 in which the resin is a liquid epoxyresin.
 3. A method according to claim 2 in which the particles ofmagnetic filler are no more than 74 microns in size.
 4. A methodaccording to claim 5 in which the ceramic magnetic filler is selectedfrom magnetic iron oxide, barium ferrite, and strontium ferrite.
 5. Themethod as recited in claim 1 wherein said magnetic filler comprisesmagnetic ceramic magnets.